Abstract: Heavy metal ions are recovered from a dilute aqueous solution by flowing the solution through either a single bed of ion-absorbing material in successive forward and reverse directions, or through a first bed of ion-absorbing material and thereafter through a second bed of ion-absorbing material in the reverse directon of flow. The reversal of flow is to periodically mechanically agitate a bed of ion-absorbing material to dislodge contaminants, such as gelatin.The method is accomplished by using one enclosed vessel, or a pair of enclosed vessels, that have valves to control the direction of flow. A timing device preferably automatically reverses the direction of flow about each hour.After a relatively large number of reversals of flow the heavy metal ions are recovered from the ion-absorbing material and the same is regenerated in the process to again absorb ions from the dilute aqueous solution.

Abstract: In the development of color negatives the same are pre-soaked in an acid-inhibited developing agent bath of typically two to four times normal concentration. Subsequent substantially normal development provides up to 21/2 stops (six times) greater sensitivity of the emulsion after photographic underexposure. Excessive contrast, grain, and fog are minimized, and necessary tracking parallelism of the contrast curves for the three layers of the color-sensitive emulsion is maintained. Deliberate underexposure in studio motion-picture-making can now be allowed, thereby to effect a highly significant saving of electrical energy in stage lighting.

Abstract: A process for treating very dilute solutions containing ecologically noxious heavy metal ions, in which the solutions are made acceptable for return to the environment, and the typically valuable heavy metal present in the solution is recovered at an economic profit. The dilute solution is flowed through an ion exchange resin, as a cross-linked polystyrene having quaternary ammonium functional groups which hold the heavy metal ions, allowing an ecologically benign effluent to return to the environment or the water to be re-used in industrial processing. Typically, an alkali metal halide is subsequently placed in contact with the resin to recover the heavy metal ion for subsequent reduction to a solid.

Abstract: Heavy metal ions are recovered from a dilute aqueous solution by flowing the solution through either a single bed of ion-absorbing material in successive forward and reverse directions, or through a first bed of ion-absorbing material and thereafter through a second bed of ion-absorbing material in the reverse direction of flow. The reversal of flow is to periodically mechanically agitate a bed of ion-absorbing material to dislodge contaminants, such as gelatin.The method is accomplished by using one enclosed vessel, or a pair of enclosed vessels, that have valves to control the direction of flow. A timing device preferably automatically reverses the direction of flow about each hour.After a relatively large number of reversals of flow the heavy metal ions are recovered from the ion-absorbing material and the same is regenerated in the process to again absorb ions from the dilute aqueous solution.